Insight into the Alkaline Stability of N‐Heterocyclic Ammonium Groups for Anion‐Exchange Polyelectrolytes

Autor:	Nanjun Chen, Chuan Hu, Hui Li, Yiqi Jin, Shaoyi Xu, Bo Wu, Young Moo Lee, Jiantao Fan, Haijun Liu
Rok vydání:	2021
Předmět:	Ion exchange General Chemistry General Medicine Catalysis Polyelectrolyte chemistry.chemical_compound Membrane chemistry Polymer chemistry Hofmann elimination Nucleophilic substitution Degradation (geology) Ammonium Degradation pathway
Zdroj:	Angewandte Chemie. 133:19421-19429
ISSN:	1521-3757 0044-8249
DOI:	10.1002/ange.202105231
Popis:	The alkaline stability of N-heterocyclic ammonium (NHA) groups is a critical topic in anion-exchange membranes (AEMs) and AEM fuel cells (AEMFCs). Here, we report a systematic study on the alkaline stability of 24 representative NHA groups at different hydration numbers (λ) at 80 °C. The results elucidate that γ-substituted NHAs containing electron-donating groups display superior alkaline stability, while electron-withdrawing substituents are detrimental to durable NHAs. Density-functional-theory calculations and experimental results suggest that nucleophilic substitution is the dominant degradation pathway in NHAs, while Hofmann elimination is the primary degradation pathway for NHA-based AEMs. Different degradation pathways determine the alkaline stability of NHAs or NHA-based AEMs. AEMFC durability (from 1 A cm-2 to 3 A cm-2 ) suggests that NHA-based AEMs are mainly subjected to Hofmann elimination under 1 A cm-2 current density for 1000 h, providing insights into the relationship between current density, λ value, and durability of NHA-based AEMs.
Databáze:	OpenAIRE
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